Method and arrangement for making sz-twisted cables

ABSTRACT

An arrangement for making cables and the like comprises an advancing arrangement for advancing an elongated bundle of strands along a predetermined path. A twisting unit positioned along the path twists the elongated bundle of strands in direction circumferentially of its elongation. A first engaging unit upstream of the twisting unit prevents the twist imparted to the bundle by the twisting unit from travelling upstream along the bundle freely past the first engaging unit, and permits advancing of the bundle along the path and relative to the first engaging unit. A second engaging unit downstream of the twisting unit prevents the twist imparted to the bundle by the twisting unit from travelling downstream along the bundle freely past the second engaging unit, and permits advancing of the bundle along the path and relative to the second engaging unit. At least one of the units is movable in direction along the path. A moving arrangement is provided for continually effecting relative movement between the testing unit and at least one of the engaging units in direction along the path and in a sense varying the degree of twist imparted to the bundle of strands by the twisting unit.

United States Patent [191 Braun [4 1 Mar. 19, 1974 [75] Inventor: Dieter Braun, Cologne, Germany [73] Assignee: Felten & Guilleaume Kabelwerke Aktiengesellschaft, Cologne, Germany 22 Filed: July 17', 1972 21 Appl. No.: 272,631

[ 30] Foreign Application Priority Data July 30, 1971 Germany 2138239 [52] U.S. Cl. 57/34 AT, 57/91, 57/156 [51] Int. Cl. H01b 13/04 [58-] Field of Search 57/34 AT, 63, 91, 156

[56] References Cited UNITED STATES PATENTS 3,645,079 '2/1972 Stoebner 57/74 AT 3,373,550 3/1968 Symonds 57/34 AT 3.4l2, 544 l1/l968 Sugi et a1 57/34 AT 3,48l,l27 12/1969 Vogelsberg... 57/34 AT 3,491,525 l/l970 Sugi .l 57/34 AT 3,507,108 4/1970 Yoshimura et al. 57/34 AT FOREIGN PATENTS OR APPLICATIONS 1,468,382 l2/l966 France 57/34 AT Primary Examiner-John Petrakes Attorney, Agent, or Firm-Michael S. Striker [5 7-] ABSTRACT An arrangement for making cables and the like comprises an advancing arrangement for advancing an elongated bundle of strands along a predetermined path. A twisting unit positioned along the path twists the elongated bundle of strands in direction circumferentially of its elongation. A first engaging unit upstream of the twisting unit prevents the twist imparted to the bundle by the twisting unit from travelling upstream along the bundle freely past the first engaging unit, and permits advancing of the bundlealong the path'and relative to the first engaging unit. A second engaging unit downstream of-the twisting unit prevents the twist imparted to the bundle by the twisting unit from travelling downstream along the bundle freely past the second engaging unit, and permits advancing of the bundle along the path and relative to the second engaging unit. At least one of the units is movable in direction along the path. A moving arrangement is provided for continually effecting relative movement between the testing unit and at least one of the engaging units in direction along the path and in a sense varying the degree of twist imparted to the bundle of strands by the twisting unit.

' 24 Claims, 6 Drawing Figures METHOD AND ARRANGEMENT FOR MAKING SZ-TWISTED CABLES BACKGROUND OF THE INVENTION The invention relates to the making of twisted cables and the like. More particularly, the invention relates to the making of twisted cables from a plurality of individual strands, which themselves may consist of a plurality of twisted wires, or the like. Still more particularly, the

, invention relates to the production of electrical com- S and Z cables consisting of a twisted bundle of strands are usually made on machines having large payout drums for the untwisted strands, a large take-up drum for the twisted cable, and a twisting unit intermediate the drums. If the twisting takes place always in a single direction (S or Z) 'circumferentially of the elongation of the cable, then the take-up drum must continuously rotate both about its longitudinal axis, and also about an axis transverse to its longitudinal axis. If this is not done, the twist imparted to the cable by the twisting unit will be undone during the winding of the cable onto the take-up drum.

In 52 twisting, by way of contrast, the twisting unit alternately twists in one and then the opposite direction, and the twisted SZ-cable can be wound onto a takeup reel which is rotating only about its longitudinal axis. This is an important improvement of the manufacturing process, because the necessary double rotation of the take-up reel in S- or Z- twisting is limited in speed by the mass of the sizable take-up reel. This places a practical limit on the speed with which the strands may be advanced through the twisting unit, and accordingly greatly limits the length of cable which can be produced per unit time by such machines.

However, SZ-twisting methods of the prior art are still possessed'of significant disadvantages. The most serious drawback of known SZ-twisting methods is the necessity for repeatedly reversing the operation of the twisting unit, so as to effect the SZ-twi'st. During the manufacture, for instance, of heavy cables composed of many relatively thick strands, the twisting force required is extremely high. The rotary components of twisting units capable of applying such forces are necessarily large and very massive. In particular, if twisting is to be carried out at a high rate, for the sake of a large output, the angular momentum achieved by the rotary components of such massive twisting units will be very substantial. It is extremely difficult to quickly reverse the direction of rotation of such massive rotary components, unless one applies to them very great braking forces. However, it is of course undesirable to apply such high braking forces over and over again during operation of the twisting unit.

52 twisting arrangements are known in the prior art which have the advantage of employing simply-rotating take-up drums, and without requiring continual reversing of the twisting unit. In one such arrangement, the bundle of strands to be twisted is conducted to an intermediate storage unit and continually paid-out from such storage unit during the twisting of the bundle. The twisting unit twists in a single direction, and the filled volume of the intermediary storage unit periodically increases and decreases, during the supply of cable for alternate S- and Z-twisting. The variation of filled volume of the intermediate storage unit in such arrangement is a function of the successive lengths of S- and Z-twisted cable sections to be produced. This prior-art arrangement constitutes an improvement in that it overcomes the need for quickly and repeatedly destroying the built-up momentum of the massive twisting unit. This arrangement is disadvantageous, however, in that the intermediate storage unit, which is alternately rotated in one and then the opposite direction, will of necessity itself have a considerable mass, leading to a practical limit on the frequency with which the rotational direction of the storage unit can be reversed, and thus again leading to a practical limit on the output capacity of the cable-making machine. Moreover, the actual mechanism within the intermediate storage unit, operative for varying the length of cable stored within the storage unit, is complicated and expensive.

Another arrangement is known in the prior art which also obviates the need for rotating the take-up drum in two directions simultaneously. In that arrangement, an elongated storage unit adapted to accommodate a fixed length of cable reverses its direction of rotation after the entire length of cable stored therein has been paidout. Again, the need for repeated and quick reversing of the motion of a massive rotarymechanism creates a need for enormous braking and accelerating forces, and places a limit on the output capacity of the machine.

SUMMARY OF THE INVENTION It is the' general object of the present invention to overcome the disadvantages associated with the prior art.

It is a more particular object to set forth a method of making SZ-twisted cables which is not characterized by the shortcomings of prior-art methods.

It is another object to provide a cable-making machine which is not characterized by the shortcomings of prior-art cable-making machines.

It is a further object to set forth a method and machine which eliminates the need for repeatedly and quickly reversing the direction of rotation of the rotary components of the twisting means.

It is still another object to set forth a method and machine which avoids the need for rotating the pay-out and/or take up drums with respect to two mutually perpendicularaxes of rotation.

It is still another object to set forth a method and machine according to which the recurrent change of twisting direction is accomplished by longitudinal recipro catory motion, as opposed to rotational reciprocatory motion. 7

It is an important object to provide a method and machine by which the change in effective twisting direction is accomplished by longitudinal reciprocatory mo- It is another object to provide a machine which is simple in construction, operates in a simple manner, and is extremely reliable.

The above objects, and others which will become more apparent hereafter, are accomplished by the provision of a novel cable-making machine and by the provision of a novel method of making SZ-twisted cables. The arrangement comprises advancing means for advancing an elongated bundle of strands along a predetermined path. Twisting means positioned along the path twists the elongated bundle of strands in direction circumferentially of its elongation. First engaging means upstream of the twisting means prevents the twist imparted to the bundle by the twisting means from travelling upstream along the bundle freely past the first engaging means, and permits advancing of the bundle along the predetermined path and relative to the first engaging means. Second engaging means downstream of the twisting means prevents the twist imparted to the bundle by the twisting means from travelling downstream along the bundle freely past the second engaging means, and permits advancing of the bundle along the predetermined path and relative to the second engaging means. The first engaging means and- /or second engaging means and/or twisting means is movable in direction along the aforementioned path, and moving means continually effects relative movement between the twisting means and at least one of the engaging means in direction along the path and in a sense varying the degree of twist imparted to the bundle of strands by the twisting means.

The invention enables the advancing and twisting of bundles of strands at extremely high speeds, resulting in a productivity per cable-making machine not hitherto achievable. The novel machine, moreover, is very simple in its principle of construction, and accordingly inexpensive to build. According to the invention, the advancement rate of the bundle of strands to be twisted and the actual twisting rate can be held constant, and the alternate S- and Z-twisting can be effected exclusively by variations in the effective length of that part of the path along which twisting actually occurs. Specifically, it is possible to produce the alternate S- and Z-twisting effect by the simple superposition of two different velocities, namely, the advancement rate of the cables and the rate of change in the length of the twisting path.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic drawing of a cable-making arrangement according to the present invention;

FIG. 2 is a cross-sectional detail view of a component of the arrangement in FIG. 1;

FIG. 3 is an end view of the component illustrated in FIG. 2;

FIG. 4 is an elevational detail view of the twisting unit shown in FIG. 1;

FIG. 5 is a sectional side view of the twisting unit of FIG. 4; and

FIG. 6 illustrates another cable-making arrangement according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates, in schematic form, a cable-making arrangement according to the present invention. A plurality of supply drums 14 is provided, each wound with a single strand 1 to be incorporated in a twisted cable. It should be understood that the use of the term strand herein implies only an elongated element. Each strand 1 may consist of a single elongated wire, or of a bundle of untwisted or twisted wires. Likewise, the strands need not be all of the same character.

Advancing means, here in the form of a driven takeup drum 15, advances a bundle of strands 1 along a predetermined path. Specifically, the bundle of strands is advanced from the supply drums 14, over guide pulleys 14a, through guide 2, through first engaging means 3, 4, 5, through twisting unit 7, through second engaging means 8, through lacing or other finishing unit 16, and finally to take-up drum 15.

The structure of first engaging means 3 is illustrated in FIGS. 2 and 3. The first engaging means comprises an end plate 4 having a plurality of apertures, one aperture for each strand of the bundle to be twisted. In the illustrated embodiment, five strands are involved. Since first engaging means 3 does not rotate relative to the path of cable advancement, any twist imparted to the cable downstream of plate 4 cannot migrate upstream along the strands themselves. The rearward portion 5 of first engaging means 3 is funnel-shaped, and serves to bring the strands together to form a tight bundle.

The twisting means 7 is illustrated in FIGS. 4 and 5. It consists of an arrangement of pulleys 9, 10, 11, l2, 13 mounted on a cable guide member of generally tubular configuration, which is rotatable by the schematically illustrated drive motor M. The pulleys include an input pulley 9 and an output pulley 10. The bundle of strands passes over pulley 9, under and around pulley 11, over and around pulley 13, then under and around pulley 12, and then over pulley 10. The entire arrangement of pulleys rotates, as a whole, about the longitudinal axis of the tubular guide member, and it is noted that the width of pulley 13 is approximately twice that of each of pulleys 11 and 12.

The second engaging means 8 is merely a cable guide, which engages the advancing cable with suffcient force to prevent untwisting, and which per se is entirely conventional.

Twisting means 7 located along the path of advancement, twists the elongated bundle of strands l in direction circumferentially of the elongation of the bundle. The first engaging means 3 is adapted to engage the advancing strands at a first engagement location upstream of the twisting means 7, and is operative to prevent the twist imparted to the bundle of strands 1 from travelling upstream along the strands and freely past the first engaging means 3. Likewise, second engaging means 8 engages the twisted bundle of strands 1 at a second engagement location downstream of the twisting means 7, and prevents the twist imparted to the bundle of strands from travelling downstream along the strands and freely past the second engaging means 8. In the illustrated embodiment, both the first engaging means 3 and the second engaging means 8 do not interfere with the actual advancement of the strands and cable, respectively.

schematically illustrated reciprocating unit R. U. converts the rotary motion of motor M into the desired longitudinal reciprocatory motion, and serves to reciprocate first engaging means 3, The conversion of rotary motion into longitudinal reciprocatory motion is so well known in engineering that no further description of the reciprocating unit is thought necessary.

In the illustrated embodiment, twisting means 7 is driven by drive means M. The mechanical connection between motor M and twisting unit 7 is indicated schematically by two meshing bevel gears 13, 14. The driving of twisting units is well known to those familiar with the art. It is noted, in particular, that the pulleys of twisting unit 7 turn about their respective axles, while the entire pulley assembly rotates, as a whole, about an axis coincident with the linear portion of the advancement path of cable 6, in the illustrated embodiment.

Twisting means 7 turns only in a single direction. For the purpose of explanation, it will be assumed that twisting means 7 effects Z-twisting of the strands as they pass from means3 to means 7, and effects 5- twisting of the strands as the strands pass downstream from means 7 to means 8. As is well known in the twisting art, if the distances between the means 3, 7 and 8 are fixed, 'then, regardless of the values of these distances, the Z-twist imparted to a particular unit length of strands as the unit length passes from means 3 to means 7 will be exactly undone as the unit length is subsequently subjected to S-twisting in passing from means 7 to means 8. Thus, regardless of the spacing between means 3, 7 and 8, if such spacing is fixed, no twisting can be effected. To demonstrate this point mathematically, let D, be the number of twists produced in a particular unit length of strands as it passes from means 3 to means 7. The numerical value of D, can be calculated as follows:

where n twisting rate of means 7 (revolutions/unit time) L, spacing between means 3 and 7 T, total time it takes a short unit length of strands to pass from means 3 to means 7. Likewise, let D be the number of twists producedin that same short unit length of strands as it passes from means-7 to means 8.'The numerical value of D can in similar fashion be calculated as i where L is the distance between means 7 and means 8. These equations can be simplified, because T and L are related by the advancement rate of the strands, v as follows:

- T L,/v,

Accordingly unit length of strands, it is only necessary to add the twists produced during the passage from means 3 to means 7 to the twists produced during the passage from means 7 to means 8 Thus it can be seen that, regardless of the actual values of L, and L the Z-twist produced in a unit length of strands during-the passage from means 3 to means 7 will' be exactly cancelled by the contrary S-twist to which that unit length is subjected during its passage from means 7 to means 8.

According to the invention, it is possible to produce a 'net twist in successive unit lengths of cable by continually varying one or both of the distances L, and L in a sense varying the degree of twist imparted to the strands as they pass along the path portion being varied. In the illustrated embodiment, the distance L is alternately increased and decreased by reciprocatory shifting of first engaging means 3, in direction of the cable path, towards and away from twisting means 7. This continual variation in the length L, between means 3 and 7 results in a corresponding variation in the number of twists produced in a particular unit length of cable as it passes from means 3 to means 8. This phenomenon will now be discussed.

Rather than considering the continual variation in twisting effect in an ongoing manner, it is conceptually simpler to consider the twisting to which a particular unit length of strands is subjected as it passes from means 3 to means 7 to means 8. In the illustrated embodiment, the distance L between means 7 and means 8 is held fixed. Thus, from the foregoing equation D nT /L it will be appreciated that no matter how means 3 is shifted relative to means 7, any unit length of cable subsequently passing between means 7 and means 8 will be subjected therebetween to a predetermined unvarying twist D which will be superimposed upon, and possibly cancel to some extent, the twist D, previously imparted to such unit length as it passed from means 3 to means 7. Thus, it is only necessary to consider in detail the nature of the twist D,.

To appreciate how the arrangement of FIG. 1 can produce a net twist in successive cable lengths, consider the following mode of operation, which is not actually preferred. The distances between means 3, 7 and 8 are held fixed, and a short unit length of cable, having a lengthu (see FIG. 1), is advanced from means 3 to means 7. Just before the length a reaches twisting means 7, it will have a certain number of Z-twists. If allowed to pass from means 7 to means 8, the length u will be subjected to an equal number of contrary S- twists, and will reach means 8 in untwisted condition.

which it will be subjected will be twice that necessary to cancel the Z-twists previously developed, and accordingly when length u reaches means 8, and thereafter take-up drum 15, it will exhibit an S-twist.

According to the invention, therefore, it is possible to achieve a net twisting of the length u without rotation of the take-up drum in a sense intended to prevent cancellation of the twist imparted upstream of the means 7. According to this exemplary mode of operation, a cancellation to zero of the twists produced in the unit length is prevented solely by longitudinal shifting of one of the engaging means.

Conversely, the reverse operation is theoretically possible. Imagine that the length u is just about to reach means 7, and that the engaging means 3 is suddenly shifted forcibly to the right, in a sense halving the distance between means 3 and 7, and in a sense squeezing" together or condensing the Z-twists intermediate means 3 and 7. In such event, the degree of Z-twist (number of Z-twists/unit length) would be doubled, and accordingly the number of Z-twists in the unit length u would be doubled. Thereafter, as length 14 passes from means 7 to means 8, the number of S-twists to which it is subjected will be only half that necessary to completely cancel the previously developed Z-twists. Thus, the unit length u will reach the take-up drum 15 exhibiting a Z-twist.

The type of first engaging means 3 used in the embodiment of FIG. 1, has a plurality of discrete paths for strands 1 (see FIG. 3) and it is not feasible to suddenly shift the engaging means 3 a great distance to the right, because the twists intermediate means 3 and 7 will offer an enormous resistance. However, it is completely feasible to shift means 3 to the right at a speed equal to or less than the advancement rate v of the strands 1, because in that event engaging means 3 can simply move with the advancing twisted length of strands. Moreover, with the type of engaging means 3 used in FIG. 1, which is the simplest type, it will indeed be necessary to shift the means 3 both towards and away from the means 7, because unlimited movement of means 3 only in direction away from means 7 is a practical impossibility, in this embodiment. In the preferred method of operation, first engaging means 3 is shifted back and forth along the path of advancement with a velocity whose magnitude is less than the advancement rate of the strands.

Continual shifting of first engaging means 3 results in continuous variation along the length of the cable of the degree of twist. That is to say, longitudinally successive short lengths of cable each have a certain average degree of twist (number of twists per unit length), and this degree of twist will vary from one short length to the next.

To repeat and summarize the preferred form of the method: The strands are advanced at an advancement rate v S-twisting takes place between means 7 and 8, while Z-twisting takes place upstream thereof, between means 3 and 7. The distance between means 3 and 7 is alternately increased and decreased, and the rates of increase and decrease are less than the advancement rate v Thus, lengths of cable strands passing from means 3 to means 7 will be Z-twisted to a degree greater or less than the subsequent degree of S-twisting, and the produced cable will accordingly consist of lengths having an S-twist alternating with lengths having a Z-twist.

FIG. 6 illustrates one possible application of an SZ- twisting arrangement according to the invention. In FIG. 6 12 single untwisted filaments 1a are twisted, in groups of four, into three twisted strands l. The SZ- twisting of each group of four filaments into a single twisted strand takes place as described above. The three twisted strands 1 are then combined into a bundle and SZ-twisted into a single cable. An advantageous feature of the arrangement schematically shown in FIG. 6 is that the longitudinal reciprocation of the three first engaging means 3a is effected in an out-of-phase manner. Accordingly, the variation of twist along the lengths of the three twisted strands of the cable is likewise out-of-phase. Particularly, for example, in the manufacture of twisted cable that is to be used in the communications industry, it has been found that such out-ofphase twist relationship contributes to the electrical de-coupling of the strands of the cable.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a particular method and apparatus for the manufacture of SZ-twisted cables, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Indeed numerous modifications are Whereas in the illustrated embodiment it is the first engaging means 3 which is reciprocated, it is likewise possible to reciprocate the second engaging means 8, instead of and or in addition to reciprocation of first engaging means 3. Of course, it is also possible, to longitudinally reciprocate the twisting unit 7 itself, but that expedient is of course less advantageous because of the much greater mass of unit 7 compared to means 3 and 8. It is further more possible to vary the speed of drive motor M during the twisting process; however, it is advantageous in that event to then vary all the other speeds involved proportionally. It is also possible, in addition to varying the distance between twisting unit 7 and one or both of means 3 and 8, to simultaneously vary the twisting speed independently of the rate of advance of the strands to be twisted, so as to in such manner supplement the variations in twist effected by longitudinal shifting.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

I. A method of making cables and the like, comprising the steps of continually advancing an elongated bundle of strands along a predetermined path at a constant advancement rate along the entire path between an inlet and an outlet thereof;

twisting said elongated bundle of strands in a predetermined direction circumferentially of the elongapossible. i

tion of said bundle at a twisting location along said path intermediate said inlet and outlet;

engaging said bundle during the advancement thereof at a first engagement location upstream of said twisting location and preventing the twist imparted to said bundle at said twisting location from travelling upstream along said bundle freely past said first engagement location to said inlet;

engaging said bundle during the advancement thereof at a second engagement location downstream of. said twisting location and preventing the twist imparted to said bundle at said twisting location from travelling downstream along said bundle freely past said second engagement location to said outlet;

and alternately increasing and decreasing the distance between at least one of said engagement locations and said twisting location, for thereby varying the degree of twist imparted to said bundle of strands during the advancement thereof along the portion of said path intermediate said twisting location and said one of said engagement locations whereby to obtain a'twisted bundle.

2. A method as defined in claim 1, wherein said step of continually advancing said strands comprises varying said constant advancement rate as a function of time, and wherein said step of increasing and decreasing comprises alternately increasing and decreasing said distance at respective rates of increase and decrease whose instantaneous magnitudes are less than the corresponding instantaneous magnitude of said advancement rate.

3. A method as defined in claim 1, wherein said step of continually advancing said bundle comprises varying said constant advancement rate as a function of time, and wherein said step of alternately increasing and decreasing comprises alternately increasing and decreasing said distance at respective rates of increase and decrease which vary in magnitude proportionally to the magnitude of said varying advancement rate.

4. A method as defined in claim 1, wherein said step of continually. advancing said bundle comprises varying said constant advancement rate as a function of time, and wherein said step of alternately increasing and decreasing comprises varying said distance at a rate of change whose magnitude varies proportionally to the magnitude of said varying advancement rate.

5. A method as defined in claim 1, further comprising the steps of combining into a single bundle a plurality of said twisted bundles, which have been twisted in an out-of-phase manner; i

and repeating said advancing, twisting, engaging and alternately, increasing and decreasing steps to thereby obtain a twisted cable having a plurality of twisted bundles in which the twist variation of each twisted bundle is oubof-phase with the twist variations of the other twisted bundles.

6. A method as defined in claim 1, wherein said step of alternately increasing and decreasing comprises alternately increasing and decreasing said distance at respective rates of increase and decrease whose magnitudes are less than the magnitude of said advancement rate.

7.-A method as defined in claim 1, wherein said step of continually advancing said bundle comprises varying said constant advancement rate as a function of time, and wherein said step of twisting comprises twisting said bundle at a varying twisting rate which varies substantially proportionally to said varying advancement rate.

8. A method as defined in claim 1, wherein said step of alternately increasing and decreasing comprises varying said distance at a rate of change whose magnitude is less than the magnitude of said advancement rate.

9. An arrangement for making cables and the like comprising, in combination, advancing means for advancing an elongated bundle of strands along a predetermined path at a constant advancement rate along the entire path between an inlet and an outlet thereof;

twisting means positioned along said path intermediate said inlet and outlet and operative for twisting such elongated bundle of strands with a predetermined speed in direction circumferentially of its elongation and in the same sense during the entire cable-making operation;

first engaging means upstream of said twisting means for preventing the twist imparted to the bundle by said twisting means from travelling upstream along the bundle freely past said first engaging means to said inlet, and for permitting advancing of the bundle along said path and relative to said first engaging means;

second engaging means downstream of said twisting means for preventing the twist imparted to the bundie by said twisting means from travelling downstream along the bundle freely past said second engaging means to said outlet, and for permitting advancing of the bundle along said path and relative to said second engaging means, at least one of said twisting means, first engaging means and second engaging means being movable in direction along said path;

and moving means for continually effecting relative movement between said twisting means and at least one of said engaging means in direction along said path and in a sense varying the degree of twist imparted to the bundle of strands by said twisting means.

10. An arrangement as defined in claim 9, wherein said first engaging means comprises guide means for guiding separate strands of an untwisted bundle of strands in direction along said path.

11. An arrangement as defined in claim 9, wherein said first engaging means comprises a guide arrangement defining a plurality of guide passages extending in direction of said path.

12. An arrangement as'defined in claim 9, wherein said first engaging means comprises a guide arrangement defining a converging plurality of guide passages extending in direction of said path.

13. An arrangement as defined in claim 9, wherein said first engaging means comprises a guide arrangement which is non-rotatable in direction circumferentially of said path and which is provided with guide passage means for guiding a bundle of strands along said path.

14. An arrangement as defined in'claim 9, wherein said twisting means is spaced in direction of said path a fixed distance from said second engaging means.

15. An arrangement as defined in claim 9, wherein said twisting means comprises a pulley arrangement.

16. An arrangement as defined in claim 9, wherein said twisting means comprises a pulley arrangement rotatable as a whole circumferentially of the direction of said path, and about a predetermined axis of rotation.

17. An arrangement as defined in claim 16, wherein said pulley arrangement comprises two guiding pulleys spaced in direction of said axis of rotation and a defleeting pulley set comprising a pulley pair located intermediate said guiding pulleys and a deflecting pulley cooperating with said pulley pair and spaced therefrom in direction transverse to said axis of rotation, said pulleys together forming a deflecting path for a bundle of strands advancing along said predetermined path.

18. An arrangement as defined in claim 17, wherein said pulley pair comprises two coaxial pulleys each having a predetermined groove width, and wherein said deflecting pulley has a groove width substantially twice said predetermined groove width.

19. An arrangement as defined in claim 18, wherein.

the respective axes of rotation of said pulleys are parallel, and further wherein the pulleys of said pulley pair lie in respective planes parallel to but displaced from said axis of rotation.

20. An arrangement as defined in claim 9; further including drive means for driving said twisting means and said moving means; and transmission means connecting said drive means to said twisting means and to said 12 moving means, respectively.

21. An arrangement as defined in claim 9, wherein said first engaging means is movable in direction along said path, and wherein said moving means comprises means for continually effecting movement of said first engaging means relative to said twisting means.

22. An arrangement as defined in claim 21, wherein said moving means comprises reciprocating means for alternately moving said first engaging means in direction along said path towards and away from said twisting means.

23. An arrangement as defined in claim 22; further including drive means for synchronously driving both said reciprocating means and said twisting means.

24. An arrangement as defined in claim 9, wherein said arrangement comprises a plurality of advancing means, a plurality of twisting means associated with respective ones of said advancing means, a plurality of first and second engaging means also respectively associated with respective ones of said plurality of advancing means, and wherein said moving means comprises means for continually effecting relative movement between each of said twisting means and at least one of the respective engaging means in an out-of-phase manner, so as to effect an out-of-phase variation in the degree of twist of each of a plurality of bundles of strands being simultaneously twisted. 

1. A method of making cables and the like, comprising the steps of continually advancing an elongated bundle of strands along a predetermined path at a constant advancement rate along the entire path between an inlet and an outlet thereof; twisting said elongated bundle of strands in a predetermined direction circumferentially of the elongation of said bundle at a twisting location along said path intermediate said inlet and outlet; engaging said bundle during the advancement thereof at a first engagement location upstream of said twisting location and preventing the twist imparted to said bundle at said twisting location from travelling upstream along said bundle freely past said first engagement location to said inlet; engaging said bundle during the advancement thereof at a second engagement location downstream of said twisting location and preventing the twist imparted to said bundle at said twisting location from travelling downstream along said bundle freely past said second engagement location to said outlet; and alternately increasing and decreasing the distance between at least one of said engagement locations and said twisting location, for thereby varying the degree of twist imparted to said bundle of strands during the advancement thereof along the portion of said path intermediate said twisting location and said one of said engagement locations whereby to obtain a twisted bundle.
 2. A method as defined in claim 1, wherein said step of continually advancing said strands comprises varying said constant advancement rate as a function of time, and wherein said step of increasing and decreasing comprises alternately increasing and decreasing said distance at respective rates of increase and decrease whose instantaneous magnitudes are less than the corresponding instantaneous magnitude of said advancement rate.
 3. A method as defined in claim 1, wherein said step of continually advancing said bundle comprises varying said constant advancement rate as a function of time, and wherein said step of alternately increasing and decreasing comprises alternately increasing and decreasing said distance at respective rates of increase and decrease which vary in magnitude proportionally to the magnitude of said varying advancement rate.
 4. A method as defined in claim 1, wherein said step of continually advancing said bundle comprises varying said constant advancement rate as a function of time, and wherein said step of alternately increasing and decreasing comprises varying said distance at a rate of change whose magnitude varies proportionally to the magnitude of said varying advancement rate.
 5. A method as defined in claim 1, further comprising the steps of combining into a single bundle a plurality of said twisted bundles, which have been twisted in an out-of-phase manner; and repeating said advancing, twisting, engaging and alternately increasing and decreasing steps to thereby obtain a twisted cable having a plurality of twisted bundles in which the twist variation of each twisted bundle is out-of-phase with the twist variations of the other twisted bundles.
 6. A method as defined in claim 1, wherein said step of alternately increasing and decreasing comprises alternately increasing and decreasing said distance at respective rates of increase and decrease whose magnitudes are less than the magnitude of said advancement rate.
 7. A method as defined in claim 1, wherein said step of continually advancing said bundle comprises varying said constant advancement rate as a function of time, and wherein said step of twisting comprises twisting said bundle at a varying twisting rate which varies substantially proportionally to said varying advancement rate.
 8. A method as defined in claim 1, wherein said step of alternately increasing and decreasing comprises varying said distance at a rate of change whose magnitude is less than the magnitude of said advancement rate.
 9. An arrangement for making cables and the like comprising, in combination, advancing means for advancing an elongated bundle of strands along a predetermined path at a constant advancement rate along the entire path between an inlet and an outlet thereof; twisting means positioned along said path intermediate said inlet and outlet and operative for twisting such elongated bundle of strands with a predetermined speed in direction circumferentially of its elongation and in the same sense during the entire cable-making operation; first engaging means upstream of said twisting means for preventing the twist imparted to the bundle by said twisting means from travelling upstream along the bundle freely past said first engaging means to said inlet, and for permitting advancing of the bundle along said path and relative to said first engaging means; second engaging means downstream of said twisting means for preventing the twist imparted to the bundle by said twisting means from travelling downstream along the bundle freely past said second engaging means to said outlet, and for permitting advancing of the bundle along said path and relative to said second engaging means, at least one of said twisting means, first engaging means and second engaging means being movable in direction along said path; and moving means for continually effecting relative movement between said twisting means and at least one of said engaging means in direction along said path and in a sense varying the degree of twist imparted to the bundle of strands by said twisting means.
 10. An arrangement as defined in claim 9, wherein said first engaging means comprises guide means for guiding separate strands of an untwisted bundle of strands in direction along said path.
 11. An arrangement as defined in claim 9, wherein said first engaging means comprises a guide arrangement defining a plurality of guide passages extending in direction of said path.
 12. An arrangement as defined in claim 9, wherein said first engaging means comprises a guide arrangement defining a converging plurality of guide passages extending in direction of said path.
 13. An arrangement as defined in claim 9, wherein said first engaging means comprises a guide arrangement which is non-rotatable in direction circumferentially of said path and which is provided with guide passage means for guiding a bundle of strands along said path.
 14. An arrangement as defined in claim 9, wherein said twisting means is spaced in direction of said path a fixed distance from said second engaging means.
 15. An arrangement as defined in claim 9, wherein said twisting means comprises a pulley arrangement.
 16. An arrangement as defined in claim 9, wherein said twisting means comprises a pulley arrangement rotatable as a whole circumferentially of the direction of said path, and about a predetermined axis of rotation.
 17. An arrangement as defined in claim 16, wherein said pulley arrangement comprises two guiding pulleys spaced in direction of said axis of rotation and a deflecting pulley set comprising a pulley pair located intermediate said guiding pulleys and a deflecting pulley cooperating with said pulley pair and spaced therefrom in direction transverse to said axis of rotation, said pulleys together forming a deflecting path foR a bundle of strands advancing along said predetermined path.
 18. An arrangement as defined in claim 17, wherein said pulley pair comprises two coaxial pulleys each having a predetermined groove width, and wherein said deflecting pulley has a groove width substantially twice said predetermined groove width.
 19. An arrangement as defined in claim 18, wherein the respective axes of rotation of said pulleys are parallel, and further wherein the pulleys of said pulley pair lie in respective planes parallel to but displaced from said axis of rotation.
 20. An arrangement as defined in claim 9; further including drive means for driving said twisting means and said moving means; and transmission means connecting said drive means to said twisting means and to said moving means, respectively.
 21. An arrangement as defined in claim 9, wherein said first engaging means is movable in direction along said path, and wherein said moving means comprises means for continually effecting movement of said first engaging means relative to said twisting means.
 22. An arrangement as defined in claim 21, wherein said moving means comprises reciprocating means for alternately moving said first engaging means in direction along said path towards and away from said twisting means.
 23. An arrangement as defined in claim 22; further including drive means for synchronously driving both said reciprocating means and said twisting means.
 24. An arrangement as defined in claim 9, wherein said arrangement comprises a plurality of advancing means, a plurality of twisting means associated with respective ones of said advancing means, a plurality of first and second engaging means also respectively associated with respective ones of said plurality of advancing means, and wherein said moving means comprises means for continually effecting relative movement between each of said twisting means and at least one of the respective engaging means in an out-of-phase manner, so as to effect an out-of-phase variation in the degree of twist of each of a plurality of bundles of strands being simultaneously twisted. 